Engineering Materials

• Low-carbon steel (mild steel)

  • An alloy that is grey and smooth, rusts if not protected
  • Ductile and tough, easy to form, braze and weld, versatile, useful for construction, nuts, bolts, bike frames
• Cast Iron

  • Dull grey, rusts easily
  • Brittle if thin, can be cast in a mould, used for manhole covers, pans and gates
• High-carbon steel (tool steel)

  • An alloy that is grey, smooth and does not rust easily
  • Hard-wearing, harder than low-carbon steel so less ductile but good for making tools, sharpens well
• Aluminium

  • Light grey with a matt finish
  • Lightweight but strong and ductile, used for drink cans, kitchen utensils and some parts in transport
• Copper

  • Rose coloured, polishes well but can oxidise to a green colour (verdigris)
  • Good electrical conductor, can be polished, welds easily, used for plumbing parts and electrical cable
• Tin

  • Silver coloured
  • Soft and malleable, easy to form, used to make food cans
• Zinc

  • Silvery blue with a matt finish
  • Brittle with average malleability and conductivity, often used to galvanise steel
• Brass

  • Non-ferrous metal that is gold coloured and darkens when oxidised with age
  • An alloy of copper and zinc, can be cast and machined, used for musical instruments and ornamental hardware
• Stainless steel

  • Ferrous metal that is silver when polished, resists rust
  • An alloy of chromium, nickel and manganese, hard and smooth, used for cutlery and sinks
• High-speed steel

  • Ferrous metal is dark grey when used for tool bits
  • Can be alloyed with a variety of materials for different properties, can withstand high temperatures, used for drill bits and saw blades
• Acrylic (PMMA) resists weather well, can be cut, folded and polished well, scratches easily, and is used for car lights, visors and baths.
• High impact polystyrene (HIPS) is a thermoforming polymer that is rigid, cheap, available in a lot of colours, and can be cut and vacuum formed easily.
• Polyethylene terephthalate (PET) is a thermoforming polymer that is clear, smooth finish, light, strong and tough, and is used for clothing and drinks bottles.
• Thermosetting polymers are good insulators and are resistant to heat and chemicals.
• Thermosetting polymers are also called ‘thermoset’ and can only be formed once as they cannot be reheated and therefore cannot be recycled.
• Polyvinyl chloride (PVC) is a thermoforming polymer that is cheap, can be matt or high gloss, brittle but durable, and can be extruded or in flat sheets, used in blister packs and window frames.
• High impact polystyrene (HIPS) is food safe but toxic when burned and is used for CD cases and yoghurt pots.
• Polypropylene (PP) is a thermoforming polymer that is easily coloured, available in sheets, tough and flexible, and is used for plastic chairs and casings.
• Acrylic (PMMA) is a thermoforming polymer that is hard, brittle, shiny, and available in a wide range of colours.
• Thermosetting polymers are brittle and can only be formed once.
• High density polythene (HDPE) is a thermoforming polymer that is stiff, strong, lightweight, lightweight and flexible, can be recycled well, and is used for washing baskets, pipes and chairs.
• • strength - the ability of a material to withstand compression, tension and shear, eg in woven fabrics cotton isn’t as strong as wool when pulled
• • hardness - the ability to withstand impact without damage, eg pine is easier to dent with an impact than oak; therefore, oak is harder
• • toughness - materials that are hard to break or snap are tough and can absorb shock, eg Kevlar in bulletproof vests is a very tough material
• • malleability - being able to bend or shape easily would make a material easily malleable, eg sheet metal such as steel or silver is malleable and can be hammered into shape
• • ductility - materials that can be stretched are ductile, eg pulling copper into wire shows it is ductile
• • elasticity - the ability to be stretched and then return to its original shape, eg elastane in swimming costumes is a highly elastic material
• Fibre glass and carbon fibre reinforced polymer (CFRP)

  • The fibres in these composite materials have a low density
  • They are strong, stiff and lightweight.
• Plywood

  • Easy to cut and finish, can be stained or painted, used for shelving, construction and toys
• Medium-density fibreboard (MDF)

  • Smooth and easy to finish, absorbs moisture so not suitable for outdoor use, used for kitchens and flat pack furniture
• Timber comes from trees, which have to grow to full maturity (between 25 and 100 years) before they can be cut down for wood.
• Clay is the raw material used in ceramics. It is found deep underground and is dug from quarries. It is a versatile material.

  Clay hardens and sets in shape when heated to high temperatures in a kiln.
• Fossil fuel

  • Fossil fuels are a finite resource, meaning that they cannot be replaced once extracted from the ground
• Examples of fossil fuels:

  • coal
  • natural gas
  • oil
• Advantages of nuclear power:

  • No harmful gases are released in the process
  • More efficient than fossil fuels
• Disadvantages of nuclear power

  • Nuclear power stations have to close after around 40 years of use when the uranium becomes less efficient at heating the water
  • Disposal of uranium is difficult and costly
  • Cost of nuclear power stations is very large
• Advantages of wind power

  • Wind energy is constantly available and sustainable
  • There is no cost for wind and the running cost of a wind turbine is relatively low
• Disadvantages of wind power

  • When there are periods of low wind, little or no energy is produced
  • They cost a lot to build and put in place
  • Some people do not like the look of wind turbines or feel that they spoil the natural landscape
• Advantages of solar power

  • Clean, renewable energy source
  • Reduces household energy bills
• Disadvantages of solar power

  • Some people do not like the look of solar panels or feel that they spoil the appearance of a building
  • Costs a lot to install
  • Does not produce much electricity when there is considerable cloud cover, during the winter months or at night